原文章地址：The Linux man-pages project
Linux User’s Manual(1) - user commands
NAME
intro - introduction to user commandsDESCRIPTION
Section 1 of the manual describes user commands and tools, for
example, file manipulation tools, shells, compilers, web browsers,
file and image viewers and editors, and so on.NOTES
Linux is a flavor of UNIX, and as a first approximation all user
commands under UNIX work precisely the same under Linux (and FreeBSD
and lots of other UNIX-like systems).
Under Linux, there are GUIs (graphical user interfaces), where you
can point and click and drag, and hopefully get work done without
first reading lots of documentation. The traditional UNIX
environment is a CLI (command line interface), where you type
commands to tell the computer what to do. That is faster and more
powerful, but requires finding out what the commands are. Below a
bare minimum, to get started.
Login
In order to start working, you probably first have to open a session
by giving your username and password. The program login(1) now
starts a shell (command interpreter) for you. In case of a graphical
login, you get a screen with menus or icons and a mouse click will
start a shell in a window. See also xterm(1).
The shell
One types commands to the shell, the command interpreter. It is not
built-in, but is just a program and you can change your shell.
Everybody has her own favorite one. The standard one is called sh.
See also ash(1), bash(1), chsh(1), csh(1), dash(1), ksh(1), zsh(1).
A session might go like:
knuth login: aeb
Password: ********
$ date
Tue Aug 6 23:50:44 CEST 2002
$ cal
August 2002
Su Mo Tu We Th Fr Sa
1 2 3
4 5 6 7 8 9 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
25 26 27 28 29 30 31
$ ls
bin tel
$ ls -l
total 2
drwxrwxr-x 2 aeb 1024 Aug 6 23:51 bin
-rw-rw-r-- 1 aeb 37 Aug 6 23:52 tel
$ cat tel
maja 0501-1136285
peter 0136-7399214
$ cp tel tel2
$ ls -l
total 3
drwxr-xr-x 2 aeb 1024 Aug 6 23:51 bin
-rw-r--r-- 1 aeb 37 Aug 6 23:52 tel
-rw-r--r-- 1 aeb 37 Aug 6 23:53 tel2
$ mv tel tel1
$ ls -l
total 3
drwxr-xr-x 2 aeb 1024 Aug 6 23:51 bin
-rw-r--r-- 1 aeb 37 Aug 6 23:52 tel1
-rw-r--r-- 1 aeb 37 Aug 6 23:53 tel2
$ diff tel1 tel2
$ rm tel1
$ grep maja tel2
maja 0501-1136285
$
Here typing Control-D ended the session.
The $ here was the command prompt—it is the shell's way of indicating
that it is ready for the next command. The prompt can be customized
in lots of ways, and one might include stuff like username, machine
name, current directory, time, and so on. An assignment PS1="What
next, master? " would change the prompt as indicated.
We see that there are commands date (that gives date and time), and
cal (that gives a calendar).
The command ls lists the contents of the current directory—it tells
you what files you have. With a -l option it gives a long listing,
that includes the owner and size and date of the file, and the
permissions people have for reading and/or changing the file. For
example, the file "tel" here is 37 bytes long, owned by aeb and the
owner can read and write it, others can only read it. Owner and
permissions can be changed by the commands chown and chmod.
The command cat will show the contents of a file. (The name is from
"concatenate and print": all files given as parameters are
concatenated and sent to "standard output" (see stdout(3)), here the
terminal screen.)
The command cp (from "copy") will copy a file.
The command mv (from "move"), on the other hand, only renames it.
The command diff lists the differences between two files. Here there
was no output because there were no differences.
The command rm (from "remove") deletes the file, and be careful! it
is gone. No wastepaper basket or anything. Deleted means lost.
The command grep (from "g/re/p") finds occurrences of a string in one
or more files. Here it finds Maja's telephone number.
Pathnames and the current directory
Files live in a large tree, the file hierarchy. Each has a pathname
describing the path from the root of the tree (which is called /) to
the file. For example, such a full pathname might be /home/aeb/tel.
Always using full pathnames would be inconvenient, and the name of a
file in the current directory may be abbreviated by giving only the
last component. That is why /home/aeb/tel can be abbreviated to tel
when the current directory is /home/aeb.
The command pwd prints the current directory.
The command cd changes the current directory.
Try alternatively cd and pwd commands and explore cd usage: "cd", "cd
.", "cd ..", "cd /" and "cd ~".
Directories
The command mkdir makes a new directory.
The command rmdir removes a directory if it is empty, and complains
otherwise.
The command find (with a rather baroque syntax) will find files with
given name or other properties. For example, "find . -name tel"
would find the file tel starting in the present directory (which is
called .). And "find / -name tel" would do the same, but starting at
the root of the tree. Large searches on a multi-GB disk will be
time-consuming, and it may be better to use locate(1).
Disks and filesystems
The command mount will attach the filesystem found on some disk (or
floppy, or CDROM or so) to the big filesystem hierarchy. And umount
detaches it again. The command df will tell you how much of your
disk is still free.
Processes
On a UNIX system many user and system processes run simultaneously.
The one you are talking to runs in the foreground, the others in the
background. The command ps will show you which processes are active
and what numbers these processes have. The command kill allows you
to get rid of them. Without option this is a friendly request:
please go away. And "kill -9" followed by the number of the process
is an immediate kill. Foreground processes can often be killed by
typing Control-C.
Getting information
There are thousands of commands, each with many options.
Traditionally commands are documented on man pages, (like this one),
so that the command "man kill" will document the use of the command
"kill" (and "man man" document the command "man"). The program man
sends the text through some pager, usually less. Hit the space bar
to get the next page, hit q to quit.
In documentation it is customary to refer to man pages by giving the
name and section number, as in man(1). Man pages are terse, and
allow you to find quickly some forgotten detail. For newcomers an
introductory text with more examples and explanations is useful.
A lot of GNU/FSF software is provided with info files. Type "info
info" for an introduction on the use of the program info.
Special topics are often treated in HOWTOs. Look in
/usr/share/doc/howto/en and use a browser if you find HTML files
there.SEE ALSO
ash(1), bash(1), chsh(1), csh(1), dash(1), ksh(1), locate(1),
login(1), man(1), xterm(1), zsh(1), wait(2), stdout(3), man-pages(7),
standards(7)COLOPHON
This page is part of release 4.11 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2015-07-23 INTRO(1)Linux User’s Manual(2) - system calls
NAME
intro - introduction to system callsDESCRIPTION
Section 2 of the manual describes the Linux system calls. A system
call is an entry point into the Linux kernel. Usually, system calls
are not invoked directly: instead, most system calls have
corresponding C library wrapper functions which perform the steps
required (e.g., trapping to kernel mode) in order to invoke the
system call. Thus, making a system call looks the same as invoking a
normal library function.
In many cases, the C library wrapper function does nothing more than:
* copying arguments and the unique system call number to the
registers where the kernel expects them;
* trapping to kernel mode, at which point the kernel does the real
work of the system call;
* setting errno if the system call returns an error number when the
kernel returns the CPU to user mode.
However, in a few cases, a wrapper function may do rather more than
this, for example, performing some preprocessing of the arguments
before trapping to kernel mode, or postprocessing of values returned
by the system call. Where this is the case, the manual pages in
Section 2 generally try to note the details of both the (usually GNU)
C library API interface and the raw system call. Most commonly, the
main DESCRIPTION will focus on the C library interface, and
differences for the system call are covered in the NOTES section.
For a list of the Linux system calls, see syscalls(2).RETURN VALUE
On error, most system calls return a negative error number (i.e., the
negated value of one of the constants described in errno(3)). The C
library wrapper hides this detail from the caller: when a system call
returns a negative value, the wrapper copies the absolute value into
the errno variable, and returns -1 as the return value of the
wrapper.
The value returned by a successful system call depends on the call.
Many system calls return 0 on success, but some can return nonzero
values from a successful call. The details are described in the
individual manual pages.
In some cases, the programmer must define a feature test macro in
order to obtain the declaration of a system call from the header file
specified in the man page SYNOPSIS section. (Where required, these
feature test macros must be defined before including any header
files.) In such cases, the required macro is described in the man
page. For further information on feature test macros, see
feature_test_macros(7).CONFORMING TO
Certain terms and abbreviations are used to indicate UNIX variants
and standards to which calls in this section conform. See
standards(7).
NOTES
Calling directly
In most cases, it is unnecessary to invoke a system call directly,
but there are times when the Standard C library does not implement a
nice wrapper function for you. In this case, the programmer must
manually invoke the system call using syscall(2). Historically, this
was also possible using one of the _syscall macros described in
_syscall(2).
Authors and copyright conditions
Look at the header of the manual page source for the author(s) and
copyright conditions. Note that these can be different from page to
page!
SEE ALSO
_syscall(2), syscall(2), syscalls(2), errno(3), intro(3),
capabilities(7), credentials(7), feature_test_macros(7),
mq_overview(7), path_resolution(7), pipe(7), pty(7), sem_overview(7),
shm_overview(7), signal(7), socket(7), standards(7), svipc(7),
symlink(7), time(7)
COLOPHON
This page is part of release 4.11 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2014-02-20 INTRO(2)Linux User’s Manual(3) - library functions
NAME
intro - introduction to library functionsDESCRIPTION
Section 3 of the manual describes all library functions excluding the
library functions (system call wrappers) described in Section 2,
which implement system calls.
Many of the functions described in the section are part of the
Standard C Library (libc). Some functions are part of other
libraries (e.g., the math library, libm, or the real-time library,
librt) in which case the manual page will indicate the linker option
needed to link against the required library (e.g., -lm and -lrt,
respectively, for the aforementioned libraries).
In some cases, the programmer must define a feature test macro in
order to obtain the declaration of a function from the header file
specified in the man page SYNOPSIS section. (Where required, these
feature test macros must be defined before including any header
files.) In such cases, the required macro is described in the man
page. For further information on feature test macros, see
feature_test_macros(7).
CONFORMING TO
Certain terms and abbreviations are used to indicate UNIX variants
and standards to which calls in this section conform. See
standards(7).
NOTES
Authors and copyright conditions
Look at the header of the manual page source for the author(s) and
copyright conditions. Note that these can be different from page to
page!
SEE ALSO
intro(2), errno(3), capabilities(7), credentials(7), environ(7),
feature_test_macros(7), libc(7), math_error(7), path_resolution(7),
pthreads(7), signal(7), standards(7)
COLOPHON
This page is part of release 4.11 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2010-11-11 INTRO(3)Linux User’s Manual(4) - special files
NAME
intro - introduction to special filesDESCRIPTION
Section 4 of the manual describes special files (devices).
FILES
/dev/* — device files
NOTES
Authors and copyright conditions
Look at the header of the manual page source for the author(s) and
copyright conditions. Note that these can be different from page to
page!
SEE ALSO
standards(7)
COLOPHON
This page is part of release 4.11 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2007-10-23 INTRO(4)Linux User’s Manual(5) - file formats and filesystems
NAME
intro - introduction to file formats and filesystemsDESCRIPTION
Section 5 of the manual describes various file formats, as well as
the corresponding C structures, if any. In addition, there are a
number of pages that document various filesystems.
NOTES
Authors and copyright conditions
Look at the header of the manual page source for the author(s) and
copyright conditions. Note that these can be different from page to
page!
SEE ALSO
standards(7)
COLOPHON
This page is part of release 4.11 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2017-03-13 INTRO(5)Linux User’s Manual(6) - games
NAME
intro - introduction to gamesDESCRIPTION
Section 6 of the manual describes all the games and funny little
programs available on the system.
NOTES
Authors and copyright conditions
Look at the header of the manual page source for the author(s) and
copyright conditions. Note that these can be different from page to
page!
COLOPHON
This page is part of release 4.11 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2007-10-23 INTRO(6)Linux User’s Manual(7) - overview, conventions, and miscellany section
NAME
intro - introduction to overview, conventions, and miscellany sectionDESCRIPTION
Section 7 of the manual provides overviews on various topics, and
describes conventions and protocols, character set standards, the
standard filesystem layout, and miscellaneous other things.
NOTES
Authors and copyright conditions
Look at the header of the manual page source for the author(s) and
copyright conditions. Note that these can be different from page to
page!
SEE ALSO
standards(7)
COLOPHON
This page is part of release 4.11 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2007-10-23 INTRO(7)Linux User’s Manual(8) - administration and privileged commands
NAME
intro - introduction to administration and privileged commandsDESCRIPTION
Section 8 of the manual describes commands which either can be or are
used only by the superuser, like system-administration commands,
daemons, and hardware-related commands.
As with the commands described in Section 1, the commands described
in this section terminate with an exit status that indicates whether
the command succeeded or failed. See intro(1) for more information.
NOTES
Authors and copyright conditions
Look at the header of the manual page source for the author(s) and
copyright conditions. Note that these can be different from page to
page!
COLOPHON
This page is part of release 4.11 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2007-10-23 INTRO(8)